This invention relates generally to refrigeration and more particularly to a new and improved chemically assisted mechanical refrigeration cycle.
The typical mechanical refrigeration system employs a mechanical compressor to raise the pressure and to condense a gaseous refrigerant, which thereafter absorbs its heat of vaporization. Thus, the typical vapor compression cycle uses an evaporator in which a liquid refrigerant, such as Freon-12, boils at a low pressure to produce cooling; a compressor to raise the pressure of the gaseous refrigerant after it leaves the evaporator; a condenser, in which the refrigerant condenses and discharges its heat to the environment; and an expansion valve through which the liquid refrigerant leaving the condenser expands from the high-pressure level in the condenser to the low pressure level in the evaporator.
Much effort has been expended over the past few decades in developing refrigeration systems which utilize low grade energy sources, such as solar energy, without the need for compressors or pumps. Much of this effort has been directed to the so-called absorption cycle, which accomplishes compression by using a secondary fluid as a solvent to absorb a refrigerant gas. A typical absorption system includes a condenser, expansion valve and evaporator, as does the vapor compression cycle. However, the compressor is replaced by an absorber-generator pair. Lithium bromide-water or water-ammonia are typical of the solvent-refrigerant mixtures used.
The resorption cycle has also been studied. Introduced in the earlier half of this century, the resorption cycle is similar in operation to the absorption cycle. However, a resorber replaces the condenser and the vapor is absorbed by a special weak solution while condensing. This solution is then circulated to the evaporator where the refrigerant boils and the heats of disassociation and vaporization produce the refrigerating effect.
Although the majority of prior systems avoid the use of compressors when using a solvent-refrigerant combination, a few processes have employed a solvent-refrigerant pair with a compressor in the system. The system and method described in U.S. Pat. No. 4,037,426 is illustrative. There the gaseous refrigerant is compressed and then mixed with liquid solvent. Thereafter, the mixture is cooled in a heat exchanger and then passed to a decanter, where the heavier liquid fraction is separated from the lighter liquid refrigerant. The liquid refrigerant then passes to a zone of low pressure where it is vaporized to absorb heat from a working fluid. Systems or methods disclosed in U.S. Pat. Nos. 3,277,659 and 4,199,961 provide other examples of compressor type systems.
These and other prior systems suffer from one or more of several limitations. For example, prior systems fail to take advantage of both the heat of vaporization and the heat of dilution to ultimately cool a working medium in a compression type cycle. Additionally, prior systems utilizing a compressor require a heavy duty compressor capable of sustaining relatively high compression ratios. Other systems operate at comparatively high pressures which require heavier duty components. Still, other systems have relatively inefficient heat transfer mechanics. Yet other systems fail to allow auxiliary heat exchange between refrigerant-solvent and solvent without decreasing the density of the flow to the compressor while other systems fail to provide sensible heat transfer in an auxiliary heat exchange between refrigerant-solvent and solvent. Still other systems fail to provide secondary evolution of gaseous refrigerant from the solvent after the solvent leaves the evaporator to facilitate overall efficiency. These and other problems encountered by the prior systems are substantially reduced, if not eliminated, by the present invention.